(navigation image)
Home American Libraries | Canadian Libraries | Universal Library | Community Texts | Project Gutenberg | Children's Library | Biodiversity Heritage Library | Additional Collections
Search: Advanced Search
Anonymous User (login or join us)
Upload
See other formats

Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

VALDEZ AND SHOUP GLACIERS                              247
the west side has fluctuated notably in volume. Part of this variation is doubtless due to fluctuation according to the season of the year.
Recession of the Glacier. Photographs taken in 1909 from sites occupied by Grant in 1905 and 1908 show that the retreat of the glacier is continuing, as is also shown by Dr. Camicia's measurements. Recent retreat is also attested by the presence of detached ice masses, partly covered with ablation moraine or with outwash gravels, some distance out from the ice front on the west side, and at several points near the center.
There is no continuous recessional moraine in front of the Valdez Glacier, the 468-foot ridge projecting from the east side of the valley, three quarters of a mile south of the glacier (Fig. 22) being a rock spur. West of the center of the glacier there is, however, an elongated morainic hillock 75 to 100 feet high. It is 850 feet from the ice front and extends parallel to it, the site of Dr. Camicia's original monument and of one of our camera stations (C, Fig. 22). On either side of it are two or three other hillocks forming a crescent. This monument ridge is made up of rounded outwash gravels and of angular scratched bowlders including many crystalline rocks, some of them large, and seems to contain no ice. The knolls to the west are chiefly dissected, outwash gravel remnants, while some of those to the east still contain ice. On these knolls are scattered shrubs ten years old or so, indicating that the year 1898, when the prospectors report some of these knolls uncovered, a condition also shown in photographs, was soon after the ice had left the monument ridge. Probably it even later abandoned some of the hills to the east which still contain ice. The rock knobs on the east side of the glacier have only annual plants growing upon them and have apparently been uncov^ ered later still. The mountain slopes on either side of the glacier also have a barren strip at their base from which the ice has recently receded.
Outwash Gravel Plain. From the glacier to the fiord, a distance of three and a half miles, extends a broad, perfectly-developed outwash gravel plain, which descends sixty feet or so to the mile. It is made up predominantly of rounded outwash gravels deposited by the glacial streams, and has a high percentage of slate fragments. There are practically no large bowlders. Over the whole surface of the plain there are numerous dry channels and low terrace strips between channels. This outwash plain has an area of about ten square miles, extending southward to Lowe River. The active aggradation by the large stream from the eastern margin of Valdez Glacier, locally known as Glacier River, has built up the gravel plain so high that a lake is held in between the outwash gravel plain, the mountain side and an east-west ridge on the north side of Lowe River. This is Robe Lake, which is over two miles long and has had one of the glacial streams flowing into it since before 1898. The outlet, Robe River, receives as tributaries several other glacial streams (PL XCV).
The outwash gravels are slumping for a half mile from the ice front near the western valley wall, and there are kettles partly filled with water, showing that buried ice extends at least this distance out from the visible terminus. East of the center other areas of slumping show buried ice beneath the gravels, though these do not extend so much as a quarter mile from the terminus. The persistent rumor in Alaska that ice underlies the whole gravel plain, and even the site of the town of Valdez, and that it has been reached by wells and pulled up by the anchors of ships, is wholly without basis; at least we have not been able to find any definite evidence of its truth.
Near the glacier there is no vegetation upon the outwash gravel plain, except upon the